CBSE Class 10 Science Practical Exam 2027: Experiments, Viva Questions, Marking Scheme

In short: CBSE Class 10 Science practical exam carries 20 marks of internal assessment. This guide covers all 15 prescribed experiments, step-by-step procedures, expected viva questions with answers, marking scheme breakdown, and tips to score full marks. Practicals are scoring — proper preparation guarantees 18-20 marks.

CBSE Class 10 Science Practical Exam Overview

Marking Scheme (20 Marks Total)

Exam Pattern

• Duration: 2 hours
• Experiments: 2 experiments (one from each section — Physics/Chemistry and Biology)
• Viva: Questions from all experiments, not just the ones performed
• Record: Must be complete and signed by teacher

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Complete List of CBSE Class 10 Science Experiments

Section A: Physics and Chemistry (8 Experiments)

Section B: Biology (7 Experiments)

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Section A Experiments — Detailed Procedures

Experiment 1: Finding pH of Samples

Aim: To find the pH of the following samples using pH paper/universal indicator:

• Dilute HCl
• Dilute NaOH
• Dilute ethanoic acid
• Lemon juice
• Water
• Dilute sodium bicarbonate solution

Materials Required:

• pH paper strips or Universal indicator
• Test tubes and test tube stand
• Dropper
• Sample solutions

Procedure:

1. Take 6 clean test tubes and label them A to F
2. Pour 2-3 ml of each sample in respective test tubes
3. Dip pH paper strip in each solution OR add 2-3 drops of universal indicator
4. Compare the color with the standard pH chart
5. Record the pH value

Observation Table:

Precautions:

• Use fresh pH paper for each sample
• Do not touch pH paper with fingers
• Compare color immediately (within 30 seconds)
• Use dilute solutions only

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Experiment 2: Properties of Acids and Bases

Aim: To study the properties of acids and bases (HCl and NaOH) by their reaction with:

• Litmus solution (red and blue)
• Zinc metal
• Solid sodium carbonate

Procedure:

A. Reaction with Litmus:

1. Take dilute HCl in a test tube, add blue litmus solution — turns red
2. Take dilute NaOH in a test tube, add red litmus solution — turns blue

B. Reaction with Zinc:

1. Take dilute HCl in a test tube, add zinc granules
2. Observe effervescence (bubbles)
3. Bring a burning matchstick near the mouth — pop sound (hydrogen gas)

C. Reaction with Sodium Carbonate:

1. Take dilute HCl in a test tube, add sodium carbonate
2. Observe brisk effervescence
3. Pass the gas through lime water — turns milky (CO₂ confirmed)

Observations:

Chemical Equations:

• Zn + 2HCl → ZnCl₂ + H₂↑
• Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑

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Experiment 3: Reaction of Metals with Acids

Aim: To study the reaction of zinc, iron, copper, and aluminium metals with dilute HCl and dilute H₂SO₄.

Procedure:

1. Take 4 test tubes, add 5 ml dilute HCl to each
2. Add small pieces of Zn, Fe, Cu, and Al to each test tube
3. Observe the reaction and rate of gas evolution
4. Repeat with dilute H₂SO₄

Observation Table:

Conclusion:

• Reactivity order: Zn > Al > Fe > Cu
• Copper does not react (below hydrogen in reactivity series)
• Aluminium has oxide layer that must be removed first

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Experiment 4: Displacement Reactions

Aim: To study displacement reactions by placing:

• Iron nail in copper sulphate solution
• Copper strip in ferrous sulphate solution

Procedure:

1. Take CuSO₄ solution in a test tube, dip clean iron nail
2. Keep for 15-20 minutes, observe color change
3. Take FeSO₄ solution in another test tube, dip copper strip
4. Observe for any change

Observations:

• Iron in CuSO₄: Blue color fades, brown deposit on nail (copper deposited)
• Copper in FeSO₄: No change observed

Equations:

• Fe + CuSO₄ → FeSO₄ + Cu (displacement occurs)
• Cu + FeSO₄ → No reaction (copper is less reactive than iron)

Conclusion: More reactive metal displaces less reactive metal from its salt solution.

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Experiment 5: Focal Length of Concave Mirror

Aim: To determine the focal length of a concave mirror by obtaining the image of a distant object.

Apparatus: Concave mirror, mirror stand, white screen, meter scale

Procedure:

1. Mount the concave mirror on the stand facing a distant object (tree, building)
2. Place the white screen in front of the mirror
3. Adjust the screen position until a sharp, inverted image is formed
4. Measure the distance between mirror and screen
5. This distance equals the focal length (f)

Theory:

• For distant object: u → ∞
• Using mirror formula: 1/f = 1/v + 1/u
• When u = ∞, v = f
• Image forms at focus

Observation Table:

Mean focal length = (15.2 + 15.0 + 15.1)/3 = 15.1 cm

Precautions:

• Mirror should be clean and dust-free
• Object should be far away (at least 50 meters)
• Screen should be perpendicular to principal axis
• Take multiple readings for accuracy

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Experiment 6: Focal Length of Convex Lens

Aim: To determine the focal length of a convex lens by obtaining the image of a distant object.

Apparatus: Convex lens, lens stand, white screen, meter scale

Procedure:

1. Mount the convex lens on the stand facing a distant object
2. Place the white screen behind the lens
3. Adjust screen until sharp, inverted image is formed
4. Measure distance between lens and screen
5. This distance equals the focal length

Theory:

• For distant object: u → ∞
• Using lens formula: 1/f = 1/v - 1/u
• When u = ∞, v = f

Observation Table:

Mean focal length = 20.0 cm

Precautions:

• Lens should be clean
• Principal axis should be horizontal
• Image should be sharp and well-defined

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Experiment 7: Refraction Through Glass Slab

Aim: To trace the path of a ray of light through a rectangular glass slab and measure the angle of incidence, angle of refraction, and angle of emergence.

Apparatus: Rectangular glass slab, drawing board, white paper, pins, protractor, scale

Procedure:

1. Place glass slab on white paper, trace its boundary (ABCD)
2. Draw normal (NN') at point O on surface AB
3. Draw incident ray at angle i (say 30°, 45°, 60°)
4. Fix two pins P₁ and P₂ on incident ray
5. Look through the slab from opposite side
6. Fix pins P₃ and P₄ such that all four pins appear in a straight line
7. Remove slab, join P₃P₄ and extend to meet CD at O'
8. Join OO' (refracted ray inside slab)
9. Measure angles i, r, and e

Observation Table:

Conclusion:

• Angle of incidence = Angle of emergence (i = e)
• Emergent ray is parallel to incident ray
• Lateral displacement occurs

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Experiment 8: Ohm's Law Verification

Aim: To study the dependence of current (I) on potential difference (V) across a resistor and determine its resistance.

Apparatus: Resistor, ammeter, voltmeter, battery, rheostat, key, connecting wires

Circuit Diagram: Connect resistor, ammeter, rheostat, key, and battery in series. Connect voltmeter in parallel across the resistor.

Procedure:

1. Connect the circuit as per diagram
2. Insert the key, adjust rheostat for minimum current
3. Note ammeter (I) and voltmeter (V) readings
4. Change rheostat position, take 5-6 readings
5. Plot V-I graph

Observation Table:

Graph: V-I graph is a straight line passing through origin.

Conclusion:

• V ∝ I (Ohm's Law verified)
• Resistance R = V/I = 5.0 Ω (constant)

Precautions:

• Connections should be tight
• Ammeter in series, voltmeter in parallel
• Start with minimum current
• Do not exceed ammeter/voltmeter range

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Section B Experiments — Biology

Experiment 9: Binary Fission in Amoeba

Aim: To study binary fission in Amoeba using permanent slides.

Materials: Permanent slide of Amoeba showing binary fission, compound microscope

Procedure:

1. Place the slide on microscope stage
2. Focus under low power (10x), then high power (40x)
3. Observe different stages of binary fission
4. Draw labeled diagrams

Observations:

• Amoeba is unicellular organism with irregular shape
• Nucleus divides first (karyokinesis)
• Cytoplasm divides next (cytokinesis)
• Two daughter Amoebae formed

Stages Observed:

1. Parent Amoeba with single nucleus
2. Nucleus elongating
3. Nucleus dividing into two
4. Cytoplasm constricting
5. Two daughter cells separating

Diagram: Draw Amoeba showing stages of binary fission with labels: nucleus, cytoplasm, pseudopodia, constriction.

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Experiment 10: Budding in Yeast

Aim: To study budding in yeast using temporary slide preparation.

Materials: Yeast culture, glass slide, cover slip, methylene blue stain, dropper, microscope

Procedure:

1. Take a drop of yeast culture on a clean slide
2. Add a drop of methylene blue stain
3. Place cover slip gently (avoid air bubbles)
4. Observe under low power, then high power
5. Identify budding yeast cells

Observations:

• Yeast cells are oval/spherical
• Small outgrowth (bud) seen on parent cell
• Bud grows, nucleus divides
• Bud may detach or remain attached (chain formation)

Diagram: Draw yeast cells showing: parent cell, bud, nucleus, cell wall, chain of buds.

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Experiment 11: Stomata in Leaf Peel

Aim: To prepare a temporary mount of a leaf peel to show stomata.

Materials: Fresh leaf (Tradescantia/Rhoeo), forceps, needle, slide, cover slip, safranin stain, water, microscope

Procedure:

1. Take a fresh leaf, fold it and tear to get thin peel from lower surface
2. Place peel in water in watch glass
3. Transfer peel to slide, add drop of safranin
4. Wait 2 minutes, wash excess stain
5. Add drop of glycerine, place cover slip
6. Observe under microscope

Observations:

• Stomata are pore-like structures
• Each stoma has two kidney-shaped guard cells
• Guard cells contain chloroplasts
• Epidermal cells surround stomata

Diagram: Draw stomata showing: guard cells, stomatal pore, epidermal cells, chloroplasts in guard cells.

Functions of Stomata:

• Gas exchange (CO₂ in, O₂ out during photosynthesis)
• Transpiration (water loss)

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Experiment 12: Homologous and Analogous Organs

Aim: To study homologous and analogous organs in plants and animals using specimens/charts.

Materials: Charts/models of forelimbs of different vertebrates, wings of birds and insects

Homologous Organs (Same origin, different function):

Common features: Same bone structure (humerus, radius, ulna, carpals, metacarpals, phalanges)

Analogous Organs (Different origin, same function):

Conclusion:

• Homologous organs indicate common ancestry (divergent evolution)
• Analogous organs indicate convergent evolution

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Experiment 13: CO₂ Released During Respiration

Aim: To demonstrate that CO₂ is released during respiration.

Materials: Conical flask, bent tube, test tube, germinating seeds, KOH solution, lime water

Procedure:

1. Take germinating seeds in a conical flask
2. Cork the flask with bent delivery tube
3. Dip the tube end in test tube containing lime water
4. Keep the setup for 1-2 hours
5. Observe lime water

Observation: Lime water turns milky.

Conclusion: Germinating seeds release CO₂ during respiration, which turns lime water milky.

Equation: Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

Control Experiment: Use boiled (dead) seeds — no change in lime water.

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Experiment 14: Dicot and Monocot Seeds

Aim: To study the external features and structure of dicot and monocot seeds.

Materials: Soaked seeds of gram (dicot) and maize (monocot), hand lens, needle, blade

Dicot Seed (Gram/Bean):

Monocot Seed (Maize):

Differences:

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Experiment 15: Parts of a Flower

Aim: To study the parts of a flower and identify its reproductive organs.

Materials: Fresh flower (hibiscus/mustard), forceps, needle, blade, hand lens

Procedure:

1. Observe the flower externally
2. Identify calyx (sepals) and corolla (petals)
3. Remove petals carefully
4. Identify androecium (stamens) and gynoecium (pistil)
5. Dissect stamen to see anther and filament
6. Cut pistil longitudinally to see ovary, ovules

Parts Identified:

Diagram: Draw labeled diagram showing all four whorls.

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Viva Questions and Answers

Chemistry Viva Questions

pH and Indicators:

1. What is pH? pH is the negative logarithm of hydrogen ion concentration. pH = -log[H⁺]

2. What is the pH range? 0 to 14. Below 7 = acidic, 7 = neutral, above 7 = basic.

3. Why does blue litmus turn red in acid? Acids release H⁺ ions which change the color of litmus dye.

4. What is a universal indicator? A mixture of indicators that shows different colors at different pH values.

5. Why is pH important in daily life? Our stomach needs pH 1-2 for digestion; blood pH must be 7.35-7.45 for survival.

Metals and Acids:

6. Why doesn't copper react with dilute HCl? Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen.

7. What gas is evolved when zinc reacts with HCl? Hydrogen gas (H₂), confirmed by pop sound with burning matchstick.

8. Why does iron react slowly compared to zinc? Zinc is more reactive than iron in the reactivity series.

9. What is a displacement reaction? A reaction where a more reactive element displaces a less reactive element from its compound.

10. Why does the blue color of CuSO₄ fade when iron nail is dipped? Iron displaces copper; Cu²⁺ (blue) is replaced by Fe²⁺ (green/colorless).

Physics Viva Questions

Mirrors and Lenses:

11. What is focal length? Distance between the pole/optical center and the principal focus.

12. Why do we use a distant object to find focal length? For distant objects, rays are parallel, and image forms exactly at focus.

13. What type of image is formed by concave mirror for distant object? Real, inverted, and highly diminished (at focus).

14. Difference between concave mirror and convex lens? Concave mirror reflects light; convex lens refracts light. Both can form real images.

15. What is lateral displacement? The perpendicular distance between incident ray and emergent ray in a glass slab.

Ohm's Law:

16. State Ohm's Law. At constant temperature, current through a conductor is directly proportional to potential difference across it. V = IR.

17. What is resistance? Opposition to the flow of current. Unit: Ohm (Ω).

18. Why is ammeter connected in series? To measure total current flowing through the circuit.

19. Why is voltmeter connected in parallel? To measure potential difference across a component without affecting current.

20. What happens to resistance if length of wire is doubled? Resistance doubles (R ∝ length).

Biology Viva Questions

Reproduction:

21. What is binary fission? Asexual reproduction where parent divides into two equal daughter cells.

22. Why is binary fission common in unicellular organisms? Simple body organization; no specialized reproductive organs needed.

23. What is budding? Asexual reproduction where a small outgrowth (bud) develops into a new organism.

24. Difference between binary fission and budding? Binary fission: equal division. Budding: unequal division, bud is smaller.

25. What are stomata? Pores on leaf surface for gas exchange and transpiration.

26. Why are stomata mostly on lower surface of leaf? To reduce water loss; lower surface has less direct sunlight.

27. What are guard cells? Specialized cells that control opening and closing of stomata.

28. What is transpiration? Loss of water vapor from aerial parts of plants through stomata.

Evolution:

29. What are homologous organs? Organs with same origin but different functions (e.g., forelimbs of vertebrates).

30. What do homologous organs indicate? Common ancestry and divergent evolution.

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Tips to Score Full Marks in Practical Exam

Before the Exam

1. Complete your practical record — All experiments with diagrams, observations, and conclusions
2. Get it signed — Teacher's signature on each experiment is mandatory
3. Revise all experiments — Not just the ones you think will come
4. Practice diagrams — Neat, labeled diagrams score extra marks
5. Prepare viva answers — Questions can come from any experiment

During the Exam

1. Read the experiment carefully — Understand what's being asked
2. Follow the procedure step by step — Don't skip steps
3. Take accurate readings — Multiple readings for better accuracy
4. Draw neat diagrams — Use pencil for diagrams, pen for labels
5. Write observations clearly — Use tables wherever possible
6. Mention precautions — Shows you understand the experiment
7. Be confident in viva — Speak clearly, don't guess if unsure

Common Mistakes to Avoid

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Practical Record Format

Standard Format for Each Experiment:

Experiment No.: ___
Date: ___

Aim: [One clear sentence]

Apparatus/Materials Required: [List all items]

Theory/Principle: [2-3 lines explaining the concept]

Procedure: [Numbered steps]

Observation Table: [Neat table with readings]

Calculation: [If applicable]

Result/Conclusion: [One sentence summarizing findings]

Precautions: [3-4 points]

Sources of Error: [2-3 points]

Diagram: [Neat, labeled diagram]

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Frequently Asked Questions

How many experiments are asked in the practical exam?

Two experiments — one from Section A (Physics/Chemistry) and one from Section B (Biology). Each carries 4 marks.

Can viva questions come from experiments not performed in the exam?

Yes. Viva questions can come from any of the 15 prescribed experiments. Prepare all experiments for viva.

What if I make a mistake during the experiment?

Inform the examiner, ask for fresh materials if needed, and redo the experiment. Honesty is appreciated. Don't try to hide mistakes.

Is the practical record checked during the exam?

Yes. The examiner checks your practical record for completeness, neatness, and teacher's signature. It carries 5 marks.

How important are diagrams in practical exam?

Very important. Neat, labeled diagrams can add 1-2 marks per experiment. Always draw diagrams even if not explicitly asked.

What should I do if I don't know a viva answer?

Say "I'm not sure" rather than guessing wrong. Examiners appreciate honesty. Try to give a related answer if possible.

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